The present invention relates to an authorization checking system for motor vehicles, in which a control unit in the motor vehicle having one or a plurality of user-transponders, in an inquiry/response dialog using identifiers in accord with each other, checks, and allows or blocks, the authorization for unlocking and locking the motor vehicle doors as well as for starting and driving the motor vehicle, and using a master-transponder, in a special-inquiry-response dialog, differing therefrom, checks, and allows or blocks, the authorization for carrying out special functions.
An authorization checking system operating for motor vehicles, that employs user-transponders and one special master-transponder, is described in European Published patent application Ser. No. 0 835 790. Authorization checking systems of this type are advantageously used as theft protection systems in motor vehicles, having access to, starting, and driving the motor vehicle only being granted to the user having a vehicle-specific user-transponder. In authorization checking systems of this type it is desirable, after loss or theft of a user-transponder, to provide for the possibility of erasing (the data from) user-transponders of this type, adapted to the vehicle as a result of a programming procedure, and of programming new and/or other available user-transponders. In this context, the master-transponder functions to reprogram the identifier for the user-transponder. However, a data exchange between master-transponder and control unit for carrying out expanded special functions is not possible.
It is an object of the present invention, in an authorization checking system of this type used as an access and start/drive authorization system, that the user (be able to) carry out further special functions in a simple manner using the master-transponder.
Since, in the event of the replacement of defective vehicle components, the loss of a user-transponder, the programming of a new user-transponder, or the modification and/or addition of a special program, an authorized service station is not always available, the user of the motor vehicle, if he is in possession of the master-transponder, can undertake these procedures himself. Since the user cannot start and drive the motor vehicle using the master-transponder, the latter can be kept separate from the motor vehicle in a theft-proof place and can be used only when necessary.
Furthermore, since all operationally relevant electronic control units of a motor vehicle, furnished with a corresponding connection for the exchange of data, and the vehicle-specific master-transponder receive a common code at the end of the assembly line and, in a suitable system design, receive their mutual identification marks, e.g., serial numbers, it is not sufficient in the case of stolen vehicles to replace only one single control unit. For this purpose, replacement components are programmed to the remaining original vehicle electronic system, in connection with the vehicle-specific master-transponder.
Further special functions, easily realizable through the use of a master-transponder designed in accordance with the present invention, are the programming of function limitations of a vehicle, for example, a maximum permitted driving distance or limited usefulness of equipment objects connected to this system, such as a mobile telephone, as well as, particularly in the case of leased motor vehicles, the reading out of relevant vehicle data. This data can be the actual driving distance, the date and time, defects as well as data in the form of an electronic trip recorder.
For noncommercial vehicle owners, an electronic trip log book can be maintained in the same manner, providing information on fuel usage, kilometers driven, or defects arising during the trip.
For all of these special functions, protection against unauthorized access is desirable, thus presupposing the master-specific special-inquiry-response dialog.